Knee Injuries
he knee is the most complex and vulnerable joint in your
body. Whether you are a professional athlete or a “weekend
warrior," knee injuries are common in activities that place stress
on the knee joint. Knee injuries tend to be most common in
sports where there is a lot of lateral motion, twisting, and pulling,
such as basketball, tennis, and football. Knees can be hyper-
extended or twisted, which can lead to tears of the ligaments
or cartilage. The result can be severe pain, swelling, and loss
of mobility. Some knee injuries can ruin promising
athletic careers.
Pittsburgh Steelers quarterback Dennis
Dixon injured his knee in a 2010 game against
Dennis Dixon, professional football player
the Tennessee Titans (Figure a). At one time, the only way to
repair a knee injury was to fully expose the knee joint. This type of
surgery was not always successful with respect to complete repair
of the injury and full recovery of function, and recovery times were
generally as long as four to six months
Today, many knee injuries can be treated using arthroscopic
knee surgery, in which a flexible microscope and micro-precision
tools are placed into the knee joint through tiny incisions. The
surgeons can remove, repair, or replace injured tissue, such as
torn cartilage (Figure b). Recovery, which is usually complete
within a month, must still be followed by two to four weeks
of physical therapy to ensure that the patient regains full
b. Arthroscopic view of an injured
knee reveals torn cartilage.
Explain w hy hyperextension of the knee
causes dam age to the anterior cruciate ligam ent.
Two patients have undergone surgery to repair the sam e type
of injury: a tear of the anterior cruciate ligam ent. O n e patient
required the traditional open-knee surgery while the second
w as able to have arthroscopic surgery. W hich of these patients
w ould be b ack to his normal activities first? Explain why.
type of fibrous joint has the thickest
layer of connective tissue?
is the function of articular cartilage in a
synovial joint?
type of synovial joint permits movement
along two axes?
in the body does flexion occur? What
type of movement opposes it?
Articulations Form Where Bones Join Together
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